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Swine Flu Fish Oil Warning

July 24, 2009 Written by JP    [Font too small?]

It’s been a dramatic day in Swine Flu news. Firstly, the CDC (Centers for Disease Control and Prevention) publicly estimated that up to 40% of all US citizens may contract this novel H1N1 virus over the next couple of years. The WHO (World Health Organization) also just released a statement warning that pregnant women, school-aged children and seniors should be on special alert because the virus appears to be “gaining momentum” in these sensitive populations. Perhaps that’s the reason why the CDC changed its prior stance on influenza vaccines earlier today. They now recommend that all children in the US (6 months – 18 years of age) receive a seasonal flu vaccine. Those are the biggest stories in the conventional press.

On the alternative health side of things, there’s another issue relating to influenza that hasn’t received much attention yet. I’m referring to the potential connection between fish, fish oil consumption and an increased risk of flu and related complications. (1,2,3)

I know what you may be thinking: “Fish oil?! I thought fish oil was supposed to be healthy! One day you say we should take it, now you’re saying it puts us at risk for Swine Flu?” Well, there is a reasonable answer, but it doesn’t come in the form of a simple “fish oil is good” or “fish oil is bad” kind of package. The truth is that eating fish and taking fish oil is very often extremely beneficial for a great number of health conditions. But there is no substance on Earth that is 100% healthy under every conceivable circumstance. Take water, for example. Drinking plenty of pure water is a healthful practice. On the other hand, drinking excessive amounts (water intoxication) can lead to serious bodily damage and even death.

The August issue of the Journal of Nutrition reports on a study conducted on two groups of mice fed either a fish oil or corn oil enriched diet. (4) All the mice were infected with the flu virus and were then examined over a two week period. Several interesting observations were made at the conclusion of the trial:

  • The mice receiving the fish oil exhibited lower levels of lung tissue inflammation. This confirms the known anti-inflammatory activity of omega-3 fatty acids found in fish.
  • However, these same mice suffered a “40% higher mortality rate”, a “70% higher lung viral load” and “a prolonged recovery period following infection”.
  • The researchers also noted a decline in NK (natural killer) cells in the spleens of the mice that were fed fish oil and a decrease in CD8+ T cells. NK cells and cytotoxic T cells are vital players in the body’s ability to deal with infections.

Other experiments dating back as far as 1999 also demonstrated immune system impairment in mice that were exposed to the flu virus while undergoing fish oil therapy. In both instances, various immune markers displayed a dysfunctional reaction to the omega-3s and there were higher viral loads and lower body weight in the fish oil vs. the control diet mice. The deleterious effect on the immune system was pinpointed as the probable reason why these mice displayed a “delayed virus clearance”. It’s interesting to note that the mice receiving the control/placebo diet were feed beef fat (tallow) and yet they fared much better. (5,6)

It appears that this unexpected reaction has to do with the anti-inflammatory effects of of EPA and DHA (the two main omega-3 fatty acids in fish oil). It is this very same effect that makes fish oil such a powerful therapeutic tool in the management of arthritis, autoimmune conditions, cancer prevention, depression, heart disease and much more. In fact, a recent study found that high intakes of EPA and DHA affect the expression of at least 1,040 different genes that are implicated in the course of cardiovascular disease and inflammatory conditions. Other laboratory research indicates that the consumption of EPA and DHA actually changes the fatty acid composition of immune cells, which, in this case, may present both positive and negative consequences. (7,8,9)

There are other examples in the medical literature that point to a potential concern in those taking high dosage fish oil. Here’s a brief overview of some negative findings with regard to omega-3s and impaired immune function:

  • A 2008 study in the Journal of Pediatric Gastroenterology and Nutrition found that children who took fish oil had fewer CD8+ and CD14+ cells. (10)
  • EPA and DHA have also been implicated in a 24% increased risk of “community-acquired pneumonia” in young and middle-aged women. Interestingly, the consumption of alpha-linolenic acid, a plant based form of omega-3s, did not pose an increased risk. (11)
  • A group of men with HIV infection showed a “trend toward a decline in CD4 cell numbers” in a 1996 experiment. However, these results have not been replicated and the benefits of fish oil in the nutritional management of HIV and AIDS is still considered a promising field of inquiry. (12,13,14)
  • Omega-3 fed guinea pigs that were infected with tuberculosis (TB) had higher levels of bacteria in their lungs in comparison to guinea pigs fed a diet rich in omega-6 fatty acids. A loss of T-cell function was noted in the fish oil fed guinea pigs. DHA was also found to reduce resistance to fungal infections in a separate study conducted in mice. (15,16)

The previous research paints a pretty grim picture about the role that high dose fish oil plays in infection risk. But there are some studies that dispute that theory as well.

  • A study from July of this year found no significant differences in CD4+/CD8+ cells or infection rates in a group of 56 patients with severe pancreatitis who were supplemented with either fish or soybean oil. (17)
  • A 2005 trial that examined the link between fat intake and pneumonia risk in men didn’t find a positive association between EPA or DHA consumption and higher rates of illness. However, there appeared to be a 31% reduced risk in those with higher alpha-linonlenic acid (ALA), a plant-based omega-3 source, found in flax seed, hemp or perilla seed oils. (18)
  • A 1996 experiment in young children found that supplementation with alpha-linolenic acid (omega-3) and linoleic acid (omega-6) decreased the number of “infective episodes” and days absent from school over the course of one winter season. (19)

The differences found in those taking EPA/DHA (fish oil) versus ALA (plant omega-3s) may be due to a more potent anti-inflammatory effect of the marine sourced omega-3s. (20,21) In other words, fish oil calms inflammation more efficiently, but may also suppress immune function as a consequence. Clinical trials that are currently underway or that will begin shortly will hopefully help to clarify this important distinction. (22,23,24)

After studying all of the information I could find, I’ve come up with this personal strategy. I plan to continue to supplement with fish and krill oil. But if I’m in a situation where I’m at an increased risk for developing an infection, I will reduce my dosage temporarily. A brand new review of 11 studies found that the typical daily dosage of fish oil is 1.8 grams of EPA and 1.2 grams of DHA. (25) But recent evidence suggests that dosages as low as 180 mg/120 mg may be adequate, especially in the short term. (26)

In instances where a dosage reduction isn’t appropriate, I would simply recommended taking extra precautions in shielding the body and supporting the immune system. Some basic recommendations for this type of action can be found in my previous Swine Flu columns.

Be well!


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18 Comments & Updates to “Swine Flu Fish Oil Warning”

  1. Oct Says:

    VERY interesting and informative article, JP. I will be reading this one again to better absorb it all.

  2. JP Says:

    Thanks, Oct!

    I hope this new information will help us all use fish oil to it’s greatest possible advantage.

    Be well!


  3. Iggy Dalrymple Says:

    HAHA, all conventional wisdom reverses every 20 to 25 years. I remember when margarine was recommended for your health and 8 out of 10 doctors smoked Camels. I’m gonna stock up on Fleischmann’s Margarine and Camels, just in case of an epidemic.

    I’ve also read dire warnings about olive oil.

    Seriously, coconut oil might help boost a needed inflammatory response.

  4. JP Says:

    *Maybe* some denatured/hydrogenated coconut oil would do the trick. I’d hold on to the fish and olive oil though. 🙂

    PS – Properly extracted coconut oil actually combats inflammation:




    Be well!


  5. ish Says:

    Very informative post!

  6. Iggy Dalrymple Says:

    Here’s article on the subject by Dr Art Ayers.

  7. JP Says:

    Thanks, Ish and Iggy!

    Be well!


  8. Marlene Affeld Says:

    Very informative post about swine flu and the possible link to fish oil. Lots of food for thought. Thanks for the post.

  9. JP Says:

    I’m happy to know it was of interest. Thanks, Marlene!

    Be well!


  10. David Says:

    Hello. I have sent your article and Dr Art Ayers article (http://tinyurl.com/FishOil-Flu) to Dr Barry Sears (www.drsears.com) team, and Dr Sears personally has answered in a mail: “Relative to the swine flu, you have to use dramatic levels of fish oil (probably 10-15 grams of EPA and DHA per day) in humans to lower the AA/EPA to less 1 in which immune function might be compromised.”

  11. JP Says:


    Thanks for making that inquiry. It’s great that Dr. Sears replied. I hope his assessment is correct.

    Be well!


  12. dave woynarowski md Says:

    Its fun to theorize and it makes us look smart but extrapolating controlled laboratory rodent studies to humans is fraught with a long history of false conclusions.
    Given the benefits of fish oil in many studies in immunocompromised humans including diabetes, HIV/AIDS, cancer, chemo and radiation Rx, and post surgical patients none of which demonstrated increases in infections and showed significant improvements in outcomes and given the fact that the bulk of our population has a skewed Omega 6 to Omega 3 ratio of 20 to 1 I would not waste a whole lot of time worrying about this theory.

    Viz plant based Omega3’s (flax chia etc) you are correct. The very reason they are not anti-inflammtory and don’t do much to further human health is because they are 18 carbon and not 22 carbons that humans need.

  13. JP Says:

    Thank you for sharing your point of view, Dave. It’s much appreciated!

    Be well!


  14. Anja Says:

    Swine flue works in different way. Swines get throw nose 🙂

  15. Dr Scott Doughman Says:

    But did you know that DHA algae oil does not have the same issues, because it is metabolized in a way that is safe and gentle without the EPA anti-immune effects while in the plasma.

  16. JP Says:

    Thank you for your pointing that out, Scott. I’d like to look into that further. Perhaps I can do a follow up column in the future. If you know of any particular studies that you think I should look at, please let me know.

    Also, can you please comment on the apparent retroconversion of DHA to EPA found in this study?


    Be well!


  17. dott Says:

    Be interesting to find out if this fish consumption connection was true of all flu-like infections, or just the swine flu. Could make the mapping of historical influenza pandemics very interesting for some enterprising epidemic grant reseachers…
    (Hint hint.)

  18. JP Says:


    That would be interesting. My hunch is that the effects of excessive omega-3 intake *could* be problematic re: many infections because of its apparent effect on immune function. I believe this is a topic I should try to update.

    Thank you for the comment and for reminding me of this issue.

    Be well!


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